Can't evade this destroyer!

[Naga]

Pertinent info
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Date- May, 1940
Sub- Type XIIB
Location- South of Spain, West of the Straits of Gibraltar.

I was pursuing a couple of unguarded surface ships headed East towards the Straits of Gibraltar when all of a sudden I hear something whiz past my periscope. I turn the periscope, and I see that my dumb sonar man had let a destroyer get to within about 800m of my sub without noticing. Needless to say, I ordered a crash dive and made an emergency turn to avoid the depth charges he drops. I went down to 100m and dropped speed to 1kt. I checked my map and saw that this destroyer was the lead escort of a convoy I was heading directly toward, but for whatever reason, this destroyer was WAY ahead of all the other ships in the convoy.


Usually, at this point, I can just dodge the depth charges he drops and wait it out until he gives up. However, because I had been pursuing some surface ships for a good long while before it attacked, I am now low on battery and have a high CO2 level.

The first thing I tried was pointing my sub directly at/away from the destroyer while it pinged me. I had never done this before, but have read about it on this forum. On all my attempts, I was within 15 degrees of being pointed directly toward/away from the destroyer. However, it still somehow saw me. I kept trying this, and I was unable to shake the destroyer via this method. However, I think I ran it out of depth charges, as it no longer drops them.

The next thing I tried was to head directly away from the convoy. I did this, and I am now out of hydrophone range of it. However, this destroyer just won't give up. It keeps pinging me and driving right over me, but it isn't dropping any more depth charges!

My sub currently has minor damage from machine gun fire from when I went to periscope depth to see what was going on. My flak cannon and deck gun have minor damage, but that is it. Can someone give me any ideas?